Speaker Wire EFHW Antennas

A while back, I challenged myself to see what kind of antennas I could make from a cheap 50-foot roll of two-conductor speaker wire. This time I made a couple of end-fed halfwave wires for the 40M and 20M bands. 

My aim with these projects is to make (nearly) full use of the 50 feet of speaker wire. I figured that would be enough for 66-foot and 34-foot radiators for the 40M and 20M bands, respectively. These dimensions work with the Hendricks SOTA Tuner (now sold by Pacific Antenna) I planned to use with them. 

Construction couldn’t be more simple:

  • Starting with 50 feet of speaker wire, separate the conductors.
  • Cut one of the wires into two lengths, 34 and 16 feet.
  • Splice the 16-foot wire onto the 50-foot wire. Now you have wires that are approximately a halfwave on 40M (66 feet) and 20M (34 feet).
  • I added spade lugs to one end of each wire. 
  • I used pieces of a used gift card to make end insulators that would allow for adjustments if needed. (See photo)
Speaker Wire EFHW Antenna diagram
Speaker Wire EFHW Antenna diagram

Of course, you’ll need an antenna coupler to match these wires to your rig. The SOTA Tuner I used worked fine, but each wire operated only on a single band. I cheated a bit and used some other scrap wire to make two short counterpoise wires, 5 feet for 40M and 3 feet for 20M. Of course, you could always use the 34-foot wire as a counterpoise for the 66-foot wire if you’d like. 

An improvised end insulator made from an old gift card. I used this so I could shorten the wire, if needed, by folding it back on itself.
An improvised end insulator made from an old gift card. I used this so I could shorten the wire, if needed, by folding it back on itself.

I haven’t tried it yet, but an L-network transmatch should allow the 66-foot wire to work on 40M, 20M, and 10M. A 49:1 transformer might also give you multiple bands with the 66-foot wire. You’ll likely need to adjust the length to obtain a match. You’re on your own here.

In the field, the SOTA Tuner provided a good match on both wires. I used the 66-foot wire as an inverted vee and the 34-foot wire as a sloper. I had no trouble making contacts on both bands with 5 watts.

Of course, you could build these antennas with any old wire. After all, it’s just wire. But, I enjoy the challenge of being constrained by the 50 feet of speaker wire. 

I have more speaker wire and more antenna ideas, so you’re going to be subjected to more of these crazy projects in the future.

73, Craig WB3GCK

3 thoughts on “Speaker Wire EFHW Antennas”

  1. I love crazy projects. Looking forward to seeing more.

    I like the way you made the end insulators. I checked out the SOTA tuner. Not a bad price, and SWR indicator/protection, too.

    Looking good!

    73 de N6BVZ/4

    Liked by 1 person

  2. I’ve used the SOTA tuner with a 70′ wire for a few years now.
    I put knots in the wire at the resonant points for the bands I use. Then just roll the wire out to the length I need.
    Also, once you have the 40 meter length rolled out, it will work for all even and odd harmonics. I use the 40 meter lemgth on 20 meters all the time.
    I nevrr could tell a difference with or without a counterpoise

    Like

    1. Thanks for your comments, Ric. Using the 40M length, I couldn’t get a decent match on 20M. I probably need to play around with the wire length.

      Like

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